Aircon / climate control and fuel consumption
Aircon / climate control and fuel consumption
Author
Discussion

UrbanSports

Original Poster:

11,321 posts

233 months

Saturday 13th July 2013
quotequote all
I've never really thought it'd make much difference but since the weather has been good and I've had the CC on pretty much all of the time, my car has gone from 42mpg to 38mpg on the same journeys, big drop that I reckon!

Anybody else in the same boat?

Willy Nilly

12,511 posts

197 months

Saturday 13th July 2013
quotequote all
I've never switched the air conditioning off in my car for long enough to find out if it makes any difference. I bought a car with air conditioning and intended to use it.

At idle the tractor seems to show an increase of 0.4 litres/hr to run the air con.

I'd be interested to know how many kw's air conditioning takes, not much is my guess.


UrbanSports

Original Poster:

11,321 posts

233 months

Saturday 13th July 2013
quotequote all
Willy Nilly said:
I've never switched the air conditioning off in my car for long enough to find out if it makes any difference. I bought a car with air conditioning and intended to use it.

At idle the tractor seems to show an increase of 0.4 litres/hr to run the air con.

I'd be interested to know how many kw's air conditioning takes, not much is my guess.
This is what I'm on about, I wouldn't have thought it'd make much difference but in my car it looks like it does.

shirt

25,478 posts

231 months

Saturday 13th July 2013
quotequote all
full blast all the time. not sure about mpg, only time i did the calcs i returned 15mpg. ho hum.

Willy Nilly

12,511 posts

197 months

Saturday 13th July 2013
quotequote all
Aren't cars supposed to use less fuel running the air conditioning that driving with the windows open? The extra drag is worse than the AC load.

EddieFelson

1,168 posts

244 months

Saturday 13th July 2013
quotequote all
My air cons on all the time.

Riley Blue

23,205 posts

256 months

Saturday 13th July 2013
quotequote all
The smaller the car, the more noticeable the effect of turning on the A/C - a 1.4 Fiesta diesel slows as if you've touched the brake.

motco

17,649 posts

276 months

Saturday 13th July 2013
quotequote all
It is said that 10-15% down is normal on most cars. Windows open up to 30-40mph, aircon thereafter is most economical apparently.

UrbanSports

Original Poster:

11,321 posts

233 months

Saturday 13th July 2013
quotequote all
Riley Blue said:
The smaller the car, the more noticeable the effect of turning on the A/C - a 1.4 Fiesta diesel slows as if you've touched the brake.
I can't detect any change in performance!

MarkP1973

100 posts

165 months

Saturday 13th July 2013
quotequote all
When it's 30 degrees outside and I'm stuck in a traffic jam with kids in the car, I couldn't give a fk even if my economy dropped to single figures, as long as it's cool inside the car.

It'd probably be almost slightly interesting to know the actual cost over the summer of having the aircon on, maybe.

TameRacingDriver

20,597 posts

302 months

Saturday 13th July 2013
quotequote all
Riley Blue said:
The smaller the car, the more noticeable the effect of turning on the A/C - a 1.4 Fiesta diesel slows as if you've touched the brake.
Depends on the car. On the GFs Corsa C 1.2, turning the air con on seems to have little effect on the way it drives.

On the Puma, the car runs noticeably worse with it on, yet that's more powerful. I tend not to use it, and just stick to 60 - 70 with the windows half down and it does a better job of keeping me cool anyway.

Carl-H

947 posts

236 months

Saturday 13th July 2013
quotequote all
I drive an EP3 civic type r and if I have the air con on I notice a huge difference in performance. Doesn't pull like crazy toward the limiter like normal. Front tyres don't try to spin through first in the dry like they do with it off. Vtec is a much softer hit.

If I'm gonna give it some I knock the a/c off.

Willy Nilly

12,511 posts

197 months

Saturday 13th July 2013
quotequote all
UrbanSports said:
Riley Blue said:
The smaller the car, the more noticeable the effect of turning on the A/C - a 1.4 Fiesta diesel slows as if you've touched the brake.
I can't detect any change in performance!
Sounds like Riley Blue is trying to cool a 40 ft reefer trailer. My car is only 89hp I can't tell when the ac kicks in.

Waugh-terfall

18,488 posts

230 months

Saturday 13th July 2013
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I don't really care either way, my parents' cars both have climate, the AC is never off. My car has a panoramic sunroof and climate, I tend to leave mine on too, even with the roof open, unless it's chilly. If I drop the windows too, I turn the AC off but leave everything else alone.

xRIEx

8,180 posts

178 months

Saturday 13th July 2013
quotequote all
Willy Nilly said:
Aren't cars supposed to use less fuel running the air conditioning that driving with the windows open? The extra drag is worse than the AC load.
motco said:
Windows open up to 30-40mph, aircon thereafter is most economical apparently.
This is what I've heard, "about 40mph" is the efficiency crossover - although of course having the windows open just increases air movement through the car, whereas AC cools the air.

steve_bmw

1,591 posts

205 months

Saturday 13th July 2013
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I just drove 350 miles with the a/c on And my 2.5 BMW returned 43.4mpg.
The bigger the engine less you see a drop in economy.

paolow

3,262 posts

288 months

Saturday 13th July 2013
quotequote all
We drove my petrol Octavia on a long run and saw 40+ mpg (verified by fill ups) and this was with the aircon on max.

The flip side is that during winter it takes seemingly a huge amount of fuel to warm up and we drop to high 20s (at least initially)

So the cold costs far more than the heat, and you can't turn the cold off...

DCLXIV

362 posts

165 months

Saturday 13th July 2013
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When at NSL, my instantaneous drops by a good 5mpg when I switch it on. However, driving with the windows down takes 10mpg off.

DaveCWK

2,418 posts

204 months

Saturday 13th July 2013
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At idle my instantaneous fuel usage is 0.17 gallons/hr. With ac compressor activated it is 0.31gallons/hr. Ac power demand is fairly constant so can be extrapolated to ccalculate affect on mpg.

hedges88

690 posts

175 months

Saturday 13th July 2013
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I think a compressor can use as much as 3-5 horsepower, at least that's what I read.

The Honda I was driving seemed unusual in that the compressor would engage for approx. 20 seconds before switching off for 10 seconds or so rather than running continuously, never driven a car that does that before